WASHINGTON — With President Donald Trump threatening to scrap a trade deal with Canada and Mexico, Sen. Rob Portman said it be "a mistake to terminate" the pact.

In a conference call with Ohio reporters Tuesday, Portman, said killing the 1993 North American Free Trade Agreement "would have a negative impact on auto workers, farmers and service providers in Ohio," adding "we should improve the agreement."

"Most of our exports from Ohio to go Canada and Mexico," said Portman, who served as U.S. Trade Representative under President George W. Bush.

Ohioans now find themselves in the unusual position of seeing their Republican senator disagree with Trump, and their Democratic senator, Sherrod Brown, says NAFTA generally has been bad for Ohio.

Portman noted that NAFTA allows manufactured goods and agriculture products to cross borders largely free of tariffs that make the products more expensive.

As trade negotiators from the United States, Canada and Mexico gathered Tuesday in Montreal for a key round of talks on whether to renew NAFTA, Trump told reporters that the talks were going "pretty well."

But in an interview last week with Reuters, Trump said he "may terminate NAFTA."

The agreement has long provoked intense opposition from organized labor which has contended that the lure of cheap labor in Mexico encouraged American manufacturers to shift production to Mexico, costing tens of thousands of jobs and ravaging old industrial centers in the Midwest.

Trump’s tough anti-NAFTA stance resonated with blue-collar workers in the key manufacturing states of Ohio, Pennsylvania, Michigan and Wisconsin. Trump’s victories in those four states allowed him to capture the presidency in 2016.

But the Business Roundtable, an organization in Washington which represents many of the nation’s largest companies, warned that scrapping NAFTA and returning to tariffs would cost 1.8 million jobs in the United States.

In particular, the major automakers claim they would be badly hurt because NAFTA essentially integrated the North American automotive market.

According to the Ohio Department of Development, Ohio companies and farmers exported $49 billion worth of goods in 2016 to Canada and Mexico, a slight dip from 2015. The state will release the 2017 statistics next month.

Portman and Brown both approved of Trump’s decision Monday to slap tariffs on imports of washing machines from South Korea, a move designed to help Whirlpool’s production facility in Clyde.

Portman said he backed the tariffs because if "other countries are not following the rules of trade, they have to be held accountable."